mides and subsequent treatment with alkoxides in the corre-
sponding alcohol or in THF. The deviating behaviour of N-(1-
aryl-2,2-dichloropent-4-enylidene)amines towards five-membered
instead of six-membered azaheterocycles was thus highlighted.
Furthermore, reaction of the afore-mentioned pyrrolinium salts
with sodium hydroxide in water afforded a new entry into 2-
aroylpyrroles via unexpected ring transformation of 1-aryl-2,2-
dichloro-3-(aziridin-2-yl)propan-1-ones, which could be isolated
as well.
Acknowledgements
Scheme 5
The authors are indebted to the “Fund for Scientific Research -
Flanders (Belgium)” (FWO-Vlaanderen) and to Ghent University
(GOA) for financial support.
in the molecule to the alkene.13 The net result comprises the elegant
conversion of an unactivated carbon–carbon double bond into an
aziridine. Most likely, aziridines 13 participate in the transforma-
tion of pyrrolinium salts 8 into 2-aroylpyrroles 14, as treatment of
these aziridines 13 with 4 equivalents of sodium hydroxide (2 M in
H2O) under reflux for one hour furnished pyrroles 14 in excellent
yield (Scheme 5). Aroylpyrroles are of biological interest, as for
example aminoacyl substituted 2- and 4-aroylpyrroles have been
reported as a new class of anticonvulsant agents.20
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Scheme 6
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In summary, a new and convenient approach towards novel
5-alkoxymethyl-2-aryl-3-chloropyrroles is disclosed based on the
electrophile-induced bromocyclization of N-(1-aryl-2,2-dichloro-
pent-4-enylidene)amines into 5-bromomethyl-1-pyrrolinium bro-
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